Besides typical photovoltaic solar systems using panels and direct current-alternating current (DC-AC) conversion units either centralized or associated to strings of panels, there is an ongoing development of systems of photovoltaic energy conversion systems that implement a distributed type of DC/DC conversion with an embedded common Maximum Power Point Tracking algorithm (MPPT) function, instead of being centralized at the input of the DC/AC conversion inverter.
Italian patent applications Nos. VA2010A000024 and VA2010A000025, both filed on Mar. 15, 2010, assigned to the present application's assignee, the contents of each hereby incorporated by reference in their entirety, disclose a photovoltaic panel generating plant implementing a distributed DC/DC conversion. These disclosures also highlight the ease with which other functions may be implemented, such as the placing of the whole plant in a safe condition whenever the main DC/AC inverter connection to the public main is switched off (either deliberately by the photovoltaic plant operator or automatically by the public main operator because of an intervening need of isolating the photovoltaic energy producing plant from the public main).
In these systems, each photovoltaic panel or module is directly connected to a DC input bus of a DC/AC inverter through an on-board electronic DC/DC converter, preferably with MPPT control, that is normally embedded in a suitably sized weatherproof junction box at the panel. This may realize a plant network having a single central node and several secondary nodes, as illustrated schematically in FIG. 1.
As described in the above-noted prior patent applications, implementation of important ancillary functions, such as, for example, monitoring the operating conditions of each single panel, disabling of single panels or of all panels (e.g., in case the so-called “anti-islanding” protection system switches off the main inverter or in case of the intervention of fire fighters) to eliminate the risk of electrocution, may require communication between the central or main inverter and the panels and therefore a dedicated communication bus, transceivers, and/or specific software for monitoring and actuating appropriate isolation switches. The so-called “photovoltaic field” may require deployment of specific additional electronic modules for managing a data transfer protocol, such as, for example, Power Line Modem (PLM) or equivalent devices as well as complex software in terms of computation, complexity, considering the eventuality of managing networks that may includes thousands of nodes.